x-y=3则-2(y-x)=?

若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 若2x=3y,则(x*x+y*y)/x*x=? (x+y)(x-y)+(x-y)平方-(x-y)(3x-y) 其中x=-2 y=3分之一 (x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)= 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 已知2x=3y,则y分之x=< >,y分之x+y=< >. (x+y)(2x-3y)=? 若3x-5y=0,则x+y/x=（）,x-y/y=（）,2x-3y/2x+3y=( ) 2x-y/x+y=4,则4x-2y/2x+2y+3x+3y/2x-y 已知方程组{(X+Y)-3(X-Y)=7,2(X+Y)+(X-Y）=-7}则(X+Y)(X-Y)= 比例线段：已知x/y=2/3,则 x/x+y= ,x-y/x+y= 要过程! x+2y分之x-y=3,则代数式,x+2y分之2（x-y)-3(x-y)分之x+2y的值为 若x+2y分之x-y=3,则代数式x+2y分之2（x-y)-3(x-y)分之x+2y的值为 若x+y=4,则多项式1/2(x+y)+4(x-y)-3（x-y）-3/2(x+y)-x+y值是（） 【2(x-y)^3-8(x-y)^2(x+y)+6y(x-y)^2】/2(x-y)^2= 已知x-y=3,求[（x+y)(x-y)-(x-y)^2+2y(x-y)]除以的值 已知3x =2y 求x/x+y+y/x-y-y²/x²-y²